Organometallic Complex, and Light-Emitting Element, Light-Emitting Device, Electronic Device and Electronic Device Using the Organometallic Complex

ABSTRACT

An object is to provide a novel organometallic complex capable of emitting phosphorescence, an organometallic complex which exhibits deep red emission, and a light-emitting element which provides deep red emission. Provided is an organometallic complex having a structure represented by the following General Formula (G1). 
     
       
         
         
             
             
         
       
     
     In the formula, R 1  R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , and R 9  represent substituents, and M is a central metal and represents either a Group 9 element or a Group 10 element.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organometallic complex. Inparticular, the present invention relates to an organometallic complexthat is capable of converting a triplet excited state into luminescence.

2. Description of the Related Art

Organic compounds are brought into an excited state by absorption oflight. Through this excited state, various reactions (photochemicalreactions) are caused in some cases, or luminescence is generated insome cases. Therefore, the organic compounds have a wide range ofapplications.

As one example of the photochemical reactions, a reaction of singletoxygen with an unsaturated organic molecule (oxygen addition) is known(see Non-patent Document 1, for example). Since the ground state ofoxygen molecules is a triplet state, oxygen molecules do not form asinglet state (singlet oxygen) when they are excited directly by light.In contrast, when oxygen molecules interact with triplet excitedmolecules other than oxygen, the oxygen molecules form singlet oxygen,thereby leading to an oxygen addition reaction. Here, the compound thatforms the triplet excited molecules by light and enables formation ofsinglet oxygen is called a photosensitizer.

Thus, formation of singlet oxygen requires a photosensitizer that canform triplet excited molecules by light. However, since the ground stateof an ordinary organic compound is a singlet state, formation of atriplet excited state by light is forbidden transition; thus, tripletexcited molecules are difficult to generate. Therefore, as thephotosensitizer, it is necessary to use a compound that can easily causeintersystem crossing from the singlet excited state to the tripletexcited state (or a compound that allows the forbidden transitionthrough excitation directly by light into the triplet excited state). Inother words, such a compound can be used as the photosensitizer and isuseful.

Further, such a compound often exhibits phosphorescence. Phosphorescencerefers to luminescence generated by transition between differentenergies in multiplicity. In an ordinary organic compound,phosphorescence refers to luminescence generated in returning from thetriplet excited state to the singlet ground state (in contrast,fluorescence refers to luminescence in returning from the singletexcited state to the singlet ground state). Application fields of acompound capable of exhibiting phosphorescence, that is, a compoundcapable of converting the triplet excited state into luminescence(hereinafter, referred to as a phosphorescent compound), include alight-emitting element including an organic compound as a light-emittingsubstance.

An example of the structure of such a light-emitting element is a simpleone in which a light-emitting layer containing an organic compound thatis a light-emitting substance is merely provided between electrodes.Light-emitting elements having such a structure can achieve thinness,lightweight, high-speed response to signals, low-voltage DC drive, andthe like. Therefore, attention has been directed to the light-emittingelements as next-generation flat panel display elements. Further,displays using such light-emitting elements are superior in contrast,image quality, and wide viewing angle.

The light-emitting element including an organic compound as alight-emitting substance has a light emission mechanism of a carrierinjection type: a voltage is applied between electrodes where alight-emitting layer is interposed, electrons and holes injected fromthe electrodes recombine to make the light-emitting substance excited,and then light is emitted in returning from the excited state to theground state. As in the case of excitation described above, types ofexcited state include a singlet excited state (S*) and a triplet excitedstate (T*). The statistical generation ratio thereof in light-emittingelements is considered to be S*:T*=1:3.

At room temperature, a compound capable of converting a singlet excitedstate to luminescence (hereinafter, referred to as a fluorescentcompound) exhibits only luminescence from the singlet excited state(fluorescence), not luminescence from the triplet excited state(phosphorescence). Therefore, the internal quantum efficiency (the ratioof generated photons to injected carriers) of a light-emitting elementincluding a fluorescent compound is assumed to have a theoretical limitof 25%, on the basis of S*:T*=1:3.

On the other hand, in the case of a light-emitting element including aphosphorescent compound described above, the internal quantum efficiencythereof can be improved to 75% to 100% in theory; i.e., the emissionefficiency thereof can be 3 to 4 times as much as that of alight-emitting element including a fluorescent compound. Therefore,light-emitting elements including a phosphorescent compound have beenactively developed in recent years in order to achieve highly-efficientlight-emitting elements (e.g., see Non-Patent Document 2).Organometallic complexes that contain iridium or the like as a centralmetal have particularly attracted attention as phosphorescent compoundsbecause of their high phosphorescence quantum yield.

REFERENCES Non-Patent Documents

-   [Non-Patent Document 1] Inoue, Haruo et al., Basic Chemistry Course    PHOTOCHEMISTRY I, pp. 106-110, Maruzen Co., Ltd.-   [Non-Patent Document 2] Zhang, Guo-Lin and five others (2004)    Gaodeng Xuexiao Huaxue Xuebao, vol. 25, No. 3, pp. 397-400.

SUMMARY OF THE INVENTION

An object of one embodiment of the present invention is to provide anovel organometallic complex capable of emitting phosphorescence byusing an organic compound, with which a variety of derivatives can beeasily synthesized, as a ligand. Another object of one embodiment of thepresent invention is to provide an organometallic complex that exhibitsdeep red emission.

One embodiment of the present invention is an organometallic complexformed by ortho-metalation of an α-naphthylpyrazine derivative, which isrepresented by General Formula (G0) below, with an ion of a metalbelonging to Group 9 or Group 10. Another embodiment of the presentinvention is an organometallic complex exhibiting deep redphosphorescence, which is formed by ortho-metalation of anα-naphthylpyrazine derivative represented by General Formula (G0) belowwith an ion of a metal belonging to Group 9 or Group 10.

Therefore, a structure of the present invention is an organometalliccomplex having a structure represented by General Formula (G1) below.

In the formula, R¹ and R² individually represent any of an alkyl grouphaving 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms,an alkylthio group having 1 to 4 carbon atoms, or an alkoxycarbonylgroup having 1 to 5 carbon atoms. R³ represents hydrogen or an alkylgroup having 1 to 4 carbon atoms. In addition, R⁴, R⁵, R⁶, R⁷, R⁸, andR⁹ individually represent any of hydrogen, an alkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogengroup, a haloalkyl group having 1 to 4 carbon atoms, or an aryl grouphaving 6 to 13 carbon atoms. A pair of adjacent substituents selectedfrom the substituents R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ may be bonded to eachother to form a saturated ring structure. M is a central metal andrepresents either a Group 9 element or a Group 10 element.

Examples of the substituents represented as R¹ to R⁹ in the aboveGeneral Formula (G1) include: a methyl group, an ethyl group, a propylgroup, an isopropyl group, a butyl group, a sec-butyl group, an isobutylgroup, a tert-butyl group, and the like, as the alkyl group having 1 to4 carbon atoms; a methoxy group, an ethoxy group, a propoxy group, anisopropoxy group, a butoxy group, a sec-butoxy group, an isobutoxygroup, a tert-butoxy group, and the like, as the alkoxy group having 1to 4 carbon atoms; a methylthio group, an ethylthio group, a propylthiogroup, an isopropylthio group, a butylthio group, a sec-butylthio group,an isobutylthio group, a tert-butylthio group, and the like, as thealkylthio group having 1 to 4 carbon atoms; a methoxycarbonyl group, anethoxycarbonyl group, a propoxycarbonyl group, an isopropoxy carbonylgroup, a butoxycarbonyl group, a sec-butoxycarbonyl group, anisobutoxycarbonyl group, a tert-butoxycarbonyl group, and the like, asthe alkoxycarbonyl group having 1 to 5 carbon atoms; a fluoro group, achloro group, a bromo group, an iodine group, and the like, as thehalogen group; a fluoromethyl group, a difluoromethyl group, atrifluoromethyl group, a chloromethyl group, a dichloromethyl group, abromomethyl group, a 2,2,2-trifluoroethyl group, a 3,3,3-trifluoropropylgroup, and the like, as the a haloalkyl group having 1 to 4 carbonatoms; a phenyl group, a tolyl group, a biphenylyl group, a fluorenylgroup, a 1-naphthyl group, a 2-naphthyl group as the aryl group having 6to 13 carbon atoms; and the like.

In General Formula (G1) above, R³ is preferably hydrogen oralternatively both R³ and R⁹ are preferably hydrogen in terms ofsynthesis yield, because such structures reduce hindrance of a pyrazinederivative. Thus, a more preferred embodiment is an organometalliccomplex having a structure represented by General Formula (G2) below.

In the formula, R¹ and R² individually represent any of an alkyl grouphaving 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms,an alkylthio group having 1 to 4 carbon atoms, or an alkoxycarbonylgroup having 1 to 5 carbon atoms. In addition, R⁴, R⁵, R⁶, R⁷, and R⁸individually represent any of hydrogen, an alkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogengroup, a haloalkyl group having 1 to 4 carbon atoms, or an aryl grouphaving 6 to 13 carbon atoms. A pair of adjacent substituents selectedfrom the substituents R⁴, R⁵, R⁶, R⁷, and R⁸ may be bonded to each otherto form a saturated ring structure. M is a central metal and representseither a Group 9 element or a Group 10 element.

In the above General Formula (G2), R⁴, R⁶, R⁷, and R⁸ are preferablyhydrogen for ease of synthesis. Thus, a more preferable structure of thepresent invention is an organometallic complex having a structurerepresented by General Formula (G3) below.

In the formula, R¹ and R² individually represent any of an alkyl grouphaving 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms,an alkylthio group having 1 to 4 carbon atoms, or an alkoxycarbonylgroup having 1 to 5 carbon atoms. In addition, R⁵ represents any ofhydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy grouphaving 1 to 4 carbon atoms, a halogen group, a haloalkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 13 carbon atoms. M is acentral metal and represents either a Group 9 element or a Group 10element.

Here, specifically, the organometallic complex having the structurerepresented by General Formula (G1) above is preferably anorganometallic complex represented by General Formula (G4) below,because of its easy synthesis.

In the formula, R¹ and R² individually represent any of an alkyl grouphaving 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms,an alkylthio group having 1 to 4 carbon atoms, or an alkoxycarbonylgroup having 1 to 5 carbon atoms. R³ represents hydrogen or an alkylgroup having 1 to 4 carbon atoms. In addition, R⁴, R⁵, R⁶, R⁷, R⁸, andR⁹ individually represent any of hydrogen, an alkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogengroup, a haloalkyl group having 1 to 4 carbon atoms, or an aryl grouphaving 6 to 13 carbon atoms. A pair of adjacent substituents selectedfrom the substituents R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ may be bonded to eachother to form a saturated ring structure. M is a central metal andrepresents either a Group 9 element or a Group 10 element. L representsa monoanionic ligand. Moreover, n is 2 when M is a Group 9 element or nis 1 when M is a Group 10 element.

Here, specifically, the organometallic complex having the structurerepresented by General Formula (G2) above is preferably anorganometallic complex represented by General Formula (G5) below,because of its easy synthesis.

In the formula, R¹ and R² individually represent any of an alkyl grouphaving 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms,an alkylthio group having 1 to 4 carbon atoms, or an alkoxycarbonylgroup having 1 to 5 carbon atoms. In addition, R⁴, R⁵, R⁶, R⁷, and R⁸individually represent any of hydrogen, an alkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogengroup, a haloalkyl group having 1 to 4 carbon atoms, or an aryl grouphaving 6 to 13 carbon atoms. A pair of adjacent substituents selectedfrom the substituents R⁴, R⁵, R⁶, R⁷, and R⁸ may be bonded to each otherto form a saturated ring structure. M is a central metal and representseither a Group 9 element or a Group 10 element. L represents amonoanionic ligand. Moreover, n is 2 when M is a Group 9 element or n is1 when M is a Group 10 element.

Specifically, the organometallic complex having the structurerepresented by General Formula (G3) above is preferably anorganometallic complex represented by General Formula (G6) below,because of its easy synthesis.

In the formula, R¹ and R² individually represent any of an alkyl grouphaving 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms,an alkylthio group having 1 to 4 carbon atoms, or an alkoxycarbonylgroup having 1 to 5 carbon atoms. In addition, R⁵ represents any ofhydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy grouphaving 1 to 4 carbon atoms, a halogen group, a haloalkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 13 carbon atoms. M is acentral metal and represents either a Group 9 element or a Group 10element. L represents a monoanionic ligand. Moreover, n is 2 when M is aGroup 9 element or n is 1 when M is a Group 10 element.

The above-described monoanionic ligand L is preferably any of amonoanionic bidentate chelate ligand having a β-diketone structure, amonoanionic bidentate chelate ligand having a carboxyl group, amonoanionic bidentate chelate ligand having a phenolic hydroxyl group,and a monoanionic bidentate chelate ligand in which two ligand elementsare both nitrogen. More preferably, the monoanionic ligand L is amonoanionic ligand represented by Structural Formulas (L1) to (L6)below. Since these ligands have high coordinative ability and can beobtained at low price, they are useful.

In the formula, R¹⁰ to R²⁹ individually represent any of hydrogen, analkyl group having 1 to 4 carbon atoms, a halogen group, a haloalkylgroup having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbonatoms, or an alkylthio group having 1 to 4 carbon atoms. In addition,A¹, A², and A³ individually represent nitrogen N or carbon C—R, and Rrepresents hydrogen, an alkyl group having 1 to 4 carbon atoms, ahalogen group, or a haloalkyl group having 1 to 4 carbon atoms.

For more efficient emission of phosphorescence, a heavy metal ispreferable as a central metal in terms of a heavy atom effect.Therefore, one feature of the present invention is that iridium orplatinum is employed as the central metal M in each of the aboveorganometallic complexes of the present invention.

Specifically, the organometallic complex having the structurerepresented by General Formula (G1) above is preferably anorganometallic complex represented by General Formula (G7) below,because of its easy synthesis.

In the formula, R¹ and R² individually represent any of an alkyl grouphaving 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms,an alkylthio group having 1 to 4 carbon atoms, or an alkoxycarbonylgroup having 1 to 5 carbon atoms. R³ represents hydrogen or an alkylgroup having 1 to 4 carbon atoms. In addition, R⁴, R⁵, R⁶, R⁷, R⁸, andR⁹ individually represent any of hydrogen, an alkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogengroup, a haloalkyl group having 1 to 4 carbon atoms, or an aryl grouphaving 6 to 12 carbon atoms. A pair of adjacent substituents selectedfrom the substituents R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ may be bonded to eachother to form a saturated ring structure. M is a central metal andrepresents either a Group 9 element or a Group 10 element. Moreover, nis 2 when M is a Group 9 element or n is 1 when M is a Group 10 element.

Specifically, the organometallic complex having the structurerepresented by General Formula (G2) above is preferably anorganometallic complex represented by General Formula (G8) below,because of its easy synthesis.

In the formula, R¹ and R² individually represent any of an alkyl grouphaving 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms,an alkylthio group having 1 to 4 carbon atoms, or an alkoxycarbonylgroup having 1 to 5 carbon atoms. In addition, R⁴, R⁵, R⁶, R⁷, and R⁸individually represent any of hydrogen, an alkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogengroup, a haloalkyl group having 1 to 4 carbon atoms, or an aryl grouphaving 6 to 12 carbon atoms. A pair of adjacent substituents selectedfrom the substituents R⁴, R⁵, R⁶, R⁷, and R⁸ may be bonded to each otherto form a saturated ring structure. M is a central metal and representseither a Group 9 element or a Group 10 element. Moreover, n is 2 when Mis a Group 9 element or n is 1 when M is a Group 10 element.

Specifically, the organometallic complex having the structurerepresented by General Formula (G3) above is preferably anorganometallic complex represented by General Formula (G9) below,because of its easy synthesis.

In the formula, R¹ and R² individually represent any of an alkyl grouphaving 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms,an alkylthio group having 1 to 4 carbon atoms, or an alkoxycarbonylgroup having 1 to 5 carbon atoms. In addition, R⁵ represents any ofhydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy grouphaving 1 to 4 carbon atoms, a halogen group, a haloalkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms. M is acentral metal and represents either a Group 9 element or a Group 10element. Moreover, n is 2 when M is a Group 9 element or n is 1 when Mis a Group 10 element.

In the organometallic complex having the structure represented by any ofGeneral Formulas (G1) to (G3) above (i.e., including the organometalliccomplexes represented by General Formulas (G4) to (G9)),α-naphthylpyrazine represented by General Formula (G0) isortho-metalated with a metal ion. Such a coordinate structure greatlycontributes to deep red phosphorescence. Thus, another embodiment of thepresent invention is a light-emitting material containing theorganometallic complex described above.

Further, the organometallic complex of the present invention is veryeffective for the following reason: the organometallic complex can emitdeep red phosphorescence, that is, it can convert triplet excitationenergy into emission and can exhibit deep red emission, and thereforehigher efficiency is possible when the organometallic complex is appliedto a light-emitting element. Thus, the present invention also includes,in its scope, a light-emitting element in which the organometalliccomplex of the present invention is used.

At this time, the organometallic complex of the present invention iseffective in use for a light-emitting substance in terms of emissionefficiency. Thus, a light-emitting element in which the organometalliccomplex of the present invention is used for a light-emitting substanceis also a feature of the present invention.

Further, the present invention includes, in its category, not only alight-emitting device having a light-emitting element but also anelectronic device having the light-emitting device. The light-emittingdevice in this specification refers to an image display device, alight-emitting device, and a light source (e.g., a lighting device). Inaddition, the light-emitting device includes, in its category, all of amodule in which a light-emitting device is connected to a connector suchas a flexible printed circuit (FPC), a tape automated bonding (TAB) tapeor a tape carrier package (TCP), a module in which a printed wiringboard is provided on the tip of a TAB tape or a TCP, and a module inwhich an integrated circuit (IC) is directly mounted on a light-emittingelement by a chip on glass (COG) method.

According to one embodiment of the present invention, a novelorganometallic complex which can emit phosphorescence can be provided byusing an organic compound with which a variety of derivatives can beeasily synthesized as a ligand. In addition, according to one embodimentof the present invention, an organometallic complex which exhibits deepred emission can be provided. Moreover, according to one embodiment ofthe present invention, a light-emitting element, a light-emittingdevice, and an electronic device in each of which an organometalliccomplex which exhibits deep red emission is included can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a light-emitting element which is one embodiment ofthe present invention.

FIG. 2 illustrates a light-emitting element which is one embodiment ofthe present invention.

FIG. 3 illustrates a light-emitting element which is one embodiment ofthe present invention.

FIGS. 4A to 4D are views illustrating a passive matrix light-emittingdevice.

FIG. 5 illustrates a passive matrix light-emitting device.

FIGS. 6A and 6B are views illustrating an active matrix light-emittingdevice.

FIGS. 7A to 7E illustrate illustrating electronic devices.

FIG. 8 illustrates lighting devices.

FIG. 9 shows a ¹H NMR chart of an organometallic complex represented byStructural Formula (100).

FIG. 10 shows an ultraviolet-visible absorption spectrum and an emissionspectrum of the organometallic complex represented by Structural Formula(100).

FIG. 11 illustrates a light-emitting element which is one embodiment ofthe present invention.

FIG. 12 shows current density-luminance characteristics oflight-emitting elements each of which is one embodiment of the presentinvention.

FIG. 13 shows voltage-luminance characteristics of the light-emittingelements each of which is one embodiment of the present invention.

FIG. 14 shows emission spectra of the light-emitting elements each ofwhich is one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments and examples of the present invention will bedescribed in detail with reference to the accompanying drawings. Notethat the present invention is not limited to the description below, andmodes and details thereof can be modified in various ways withoutdeparting from the spirit and the scope of the present invention.Therefore, the present invention should not be construed as beinglimited to the description of the following embodiments and examples.

Embodiment 1

In Embodiment 1, an organometallic complex which is one embodiment ofthe present invention will be described.

Synthesis Method of α-Naphthylpyrazine Derivative Represented by GeneralFormula (G0)

The α-naphthylpyrazine derivative represented by General Formula (G0)below can be synthesized by a simple synthesis scheme as describedbelow. The α-naphthylpyrazine derivative can be obtained, for example,by a reaction between a lithium compound of α-naphthyl or a Grignardreagent of α-naphthyl (A1) and a pyrazine compound (A2) as shown inScheme (a) below. Alternatively, the α-naphthylpyrazine derivative canbe obtained by coupling of boronic acid of α-naphthyl compound (A1′) anda halogenated pyrazine compound (A2′) as shown in Scheme (a′) below.Further alternatively, the α-naphthylpyrazine derivative can be obtainedby a reaction between diketone of α-naphthyl compound (A1″) and diamine(A2″) as shown in Scheme (a″) below. Note that in the formula, Xrepresents a halogen element.

Since the above compounds (A1), (A2), (A1′), (A2′), (A1″), and (A2″) arecommercially available as a wide variety of compounds or can besynthesized, it is possible to synthesize many kinds ofα-naphthylpyrazine derivatives represented by General Formula (G0).Thus, a feature of the organometallic complex which is one embodiment ofthe present invention is the abundance of ligand variations.

Synthesis Method of Organometallic Complex Represented by GeneralFormula (G4))

Next described are an organometallic complex represented by GeneralFormula (G4) below and an organometallic complex represented by GeneralFormula (G7), which are specific preferable examples of anorganometallic complex of one embodiment of the present invention formedby ortho-metallation of the α-naphthylpyrazine derivative represented byGeneral Formula (G0), i.e., an organometallic complex having a structurerepresented by General Formula (G1) below.

First, as shown in Synthesis Scheme (b) below, the α-naphthylpyrazinederivative represented by General Formula (G0) and a compound of a metalbelonging to Group 9 or Group 10 which contains halogen (a metal halideor a metal complex) are heated with an alcohol solvent (e.g., glycerol,ethyleneglycol, 2-methoxyethanol, or 2-ethoxyethanol) alone or a mixedsolvent of water and one or more kinds of alcohol solvents, whereby abinuclear complex (B), which is a kind of organometallic complexeshaving the structure represented by General Formula (G1), can beobtained.

As the compound of a metal belonging to Group 9 or Group 10, whichcontains halogen, rhodium chloride hydrate, palladium chloride, iridiumchloride hydrate, iridium chloride hydrochloride hydrate, potassiumtetrachloroplatinate(II), and the like are given; however, the presentinvention is not limited to these examples. Note that in SynthesisScheme (b) below, M represents a Group 9 element or Group 10, and Xrepresents a halogen element. In addition, n is 2 when M is a Group 9element or n is 1 when M is a Group 10 element.

Furthermore, as shown in Synthesis Scheme (c) below, the dinuclearcomplex (B) obtained by the above Synthesis Scheme (b) is reacted withFM that is a material of a monoanionic ligand, whereby a proton of HL iseliminated to be coordinated to the central metal M, giving theorganometallic complex which is one embodiment of the present inventionrepresented by General Formula (G4). Note that, in Synthesis Scheme (c),M represents a Group 9 element or Group 10, and X represents a halogenelement. In addition, n is 2 when M is a Group 9 element or n is 1 whenM is a Group 10 element.

In General Formula (G4), R¹ and R² individually represent any of analkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4carbon atoms, an alkylthio group having 1 to 4 carbon atoms, or analkoxycarbonyl group having 1 to 5 carbon atoms. R³ represents hydrogenor an alkyl group having 1 to 4 carbon atoms. In addition, R⁴, R⁵, R⁶,R⁷, R⁸, and R⁹ individually represent any of hydrogen, an alkyl grouphaving 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms,a halogen group, a haloalkyl group, or an aryl group having 6 to 12carbon atoms. A pair of adjacent substituents selected from thesubstituents R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ may be bonded to each other toform an unsaturated ring structure. M is a central metal and representseither a Group 9 element or a Group 10 element. L represents amonoanionic ligand. Moreover, n is 2 when M is a Group 9 element or n is1 when M is a Group 10 element. When R¹ and R² is not hydrogen but anysubstituent such as an alkyl group having 1 to 4 carbon atoms, an alkoxygroup having 1 to 4 carbon atoms, an alkylthio group having 1 to 4carbon atoms, or an alkoxycarbonyl group having 1 to 5 carbon atom,decomposition reaction in Scheme (c) can be suppressed, whereby theyield is improved.

The monoanionic ligand (L) in General Formula (G4) is any of amonoanionic bidentate chelate ligand having a β-diketone structure, amonoanionic bidentate chelate ligand having a carboxyl group, amonoanionic bidentate chelate ligand having a phenolic hydroxyl group,or a monoanionic bidentate chelate ligand in which two ligand elementsare both nitrogen.

Further, the monoanionic ligand (L) in General Formula (G4) isrepresented by any of Structural Formulas (L1) to (L6) below.

In the formula, R¹⁰ to R²⁹ individually represent any of hydrogen, analkyl group having 1 to 4 carbon atoms, a halogen group, a haloalkylgroup, an alkoxy group having 1 to 4 carbon atoms, or an alkylthio grouphaving 1 to 4 carbon atoms. In addition, A¹, A², and A³ individuallyrepresent nitrogen N or carbon C—R, and R represents hydrogen, an alkylgroup having 1 to 4 carbon atoms, a halogen group, or a haloalkyl grouphaving 1 to 4 carbon atoms.

The organometallic complex of one embodiment of the present invention,which is represented by the above General Formula (G7), can besynthesized according to Synthesis Scheme (d) below. In other words, theorganometallic complex can be obtained by heating the organometalliccomplex represented by General Formula (G4) which is obtained by theabove Synthesis Scheme (c) and the α-naphthylpyrazine derivativerepresented by General Formula (G0) in a high boiling solvent such asglycerin at a high temperature of about 200° C. Note that, in SynthesisScheme (d), M represents a Group 9 element or Group 10, and X representsa halogen element. In addition, n is 2 when M is a Group 9 element or nis 1 when M is a Group 10 element.

In the above General Formula (G7), R¹ and R² individually represent anyof an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1to 4 carbon atoms, an alkylthio group having 1 to 4 carbon atoms, or analkoxycarbonyl group having 1 to 5 carbon atoms. R³ represents hydrogenor an alkyl group having 1 to 4 carbon atoms. In addition, R⁴, R⁵, R⁶,R⁷, R⁸, and R⁹ individually represent any of hydrogen, an alkyl grouphaving 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms,a halogen group, a haloalkyl group, or an aryl group having 6 to 12carbon atoms. A pair of adjacent substituents selected from thesubstituents R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ may be bonded to each other toform a saturated ring structure. M is a central metal and representseither a Group 9 element or a Group 10 element. Moreover, n is 2 when Mis a Group 9 element or n is 1 when M is a Group 10 element.

The organometallic complex which is one embodiment of the presentinvention is formed by combining the central metal M and the monoanionicligand L described above as appropriate. Hereinafter, specificstructural formulas of organometallic complexes each of which is oneembodiment of the present invention are given (Structural Formulas (100)to (140) below). However, the present invention is not limited thereto.

Note that geometrical isomers and stereoisomers which can exist in eachof the organometallic complexes represented by the above StructuralFormulas (100) to (140) depend on the type of ligand. The organometalliccomplex of the present invention includes all of these isomers.

Further, the above-described organometallic complexes each of which isone embodiment of the present invention can be used as a photosensitizerowing to its capability of intersystem crossing. In addition, theorganometallic complexes are capable of emitting phosphorescence, andtherefore can be used as a light-emitting material or a light-emittingsubstance for a light-emitting element.

Embodiment 2

In this embodiment, as one embodiment of the present invention, alight-emitting element in which an organometallic complex is used for alight-emitting layer will be described with reference to FIG. 1.

FIG. 1 illustrates a light-emitting element in which an EL layer 102including a light-emitting layer 113 is interposed between a firstelectrode 101 and a second electrode 103. The light-emitting layer 113contains the organometallic complex which is one embodiment of thepresent invention, which has been described in Embodiment 1.

By application of a voltage to such a light-emitting element, holesinjected from the first electrode 101 side and electrons injected fromthe second electrode 103 side recombine in the light-emitting layer 113to bring the organometallic complex into an excited state. Light isemitted when the organometallic complex in the excited state returns tothe ground state. Thus, the organometallic complex which is oneembodiment of the present invention functions as a light-emittingsubstance in the light-emitting element. Note that, in thelight-emitting element described in this embodiment, the first electrode101 functions as an anode and the second electrode 103 functions as acathode.

When the first electrode 101 functions as an anode, it is preferablyformed using a metal, an alloy, an electrically-conductive compound, amixture thereof, or the like each having a high work function(specifically, a work function of 4.0 eV or more). Specifically, forexample, indium tin oxide (ITO), indium tin oxide containing silicon orsilicon oxide, indium zinc oxide (IZO), indium oxide containing tungstenoxide and zinc oxide, and the like can be given. Other than the above,gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr),molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd),titanium (Ti), or the like can be used.

Note that, in the case where in the EL layer 102, a layer formed incontact with the first electrode 101 is formed using a compositematerial in which an organic compound and an electron acceptor(acceptor) which are described later are mixed, the first electrode 101can be formed using any of various types of metals, alloys, andelectrically-conductive compounds, a mixture thereof, and the likeregardless of the work function. For example, aluminum (Al), silver(Ag), an alloy containing aluminum (e.g., AlSi), or the like can beused.

The first electrode 101 can be formed by, for example, a sputteringmethod, an evaporation method (e.g., a vacuum evaporation method), orthe like.

The EL layer 102 formed over the first electrode 101 includes at leastthe light-emitting layer 113 and contains an organometallic complexwhich is one embodiment of the present invention. For part of the ELlayer 102, a known substance can be used, and either a low molecularcompound or a high molecular compound can be used. Note that thesubstance used for forming the EL layer 102 may have not only astructure formed of only an organic compound but also a structure inwhich an inorganic compound is partially contained.

Further, as illustrated in FIG. 1, the EL layer 102 is formed bystacking as appropriate a hole-injection layer 111 containing asubstance having a high hole-transport property, a hole-transport layer112 containing a substance having a high hole-transport property, anelectron-transport layer 114 containing a substance having a highelectron-transport property, an electron-injection layer 115 containinga substance having a high electron-injection property, and the like inaddition to the light-emitting layer 113.

The hole-injection layer 111 is a layer containing a substance having ahigh hole-injection property. As the substance having a highhole-injection property, metal oxide such as molybdenum oxide, titaniumoxide, vanadium oxide, rhenium oxide, ruthenium oxide, chromium oxide,zirconium oxide, hafnium oxide, tantalum oxide, silver oxide, tungstenoxide, or manganese oxide can be used. Alternatively, a phthalocyaninecompound such as phthalocyanine (abbreviation: H₂Pc), copper(II)phthalocyanine (abbreviation: CuPc), or vanadyl phthalocyanine(abbreviation: VOPc) can be used.

Alternatively, the following aromatic amine compounds which are lowmolecular organic compounds can be used:4,4′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MIDATA),4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB),4,4′-bis(N-{4-[N′-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl(abbreviation: DNTPD),1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene(abbreviation: DPA3B),3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2),3-[N-(1-naphtyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1), or the like.

Further alternatively, a high molecular compound (e.g., an oligomer, adendrimer, or a polymer) can be used. For example, a high molecularcompound such as poly(N-vinylcarbazole) (abbreviation: PVK),poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine (abbreviation:poly-TPD) can be given. Further alternatively, a high molecular compounddoped with acid, such aspoly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS)or polyanline/poly(styrenesulfonic acid) (PAni/PSS) can be used.

A composite material in which an organic compound and an electronacceptor (acceptor) are mixed may be used for the hole-injection layer111. Such a composite material is excellent in a hole-injection propertyand a hole-transport property because holes are generated in the organiccompound by the electron acceptor. In this case, the organic compound ispreferably a material excellent in transporting the generated holes (asubstance having a high hole-transport property).

As the organic compound used for the composite material, a variety ofcompounds such as an aromatic amine compound, a carbazole derivative, anaromatic hydrocarbon, and a high molecular compound (e.g., an oligomer,a dendrimer, or a polymer) can be used. Note that the organic compoundused for the composite material preferably has a high hole-transportproperty. Specifically, a substance having a hole mobility of 10⁻⁶cm²/Vs or more is preferable. However, materials other than these mayalternatively be used as long as they have a hole-transport propertyhigher than an electron-transport property. Specific examples of theorganic compound that can be used for the composite material will begiven below.

As the organic compound that can be used for the composite material, forexample, an aromatic amine compound such as TDATA, MIDATA, DPAB, DNTPD,DPA3B, PCzPCA1, PCzPCA2, PCzPCN1,4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD), orN,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD); and a carbazole derivative such as4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB),9-[4-(N-carbazolyl)]phenyl-10-phenylanthracene (abbreviation: CzPA), or1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene can be used.

Alternatively, an aromatic hydrocarbon compound such as2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),2-tert-butyl-9,10-di(1-naphthyl)anthracene,9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA),2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA),9,10-di(2-naphthyl)anthracene (abbreviation: DNA),9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene(abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene(abbreviation: DMNA),9,10-bis[2-(1-naphthyl)phenyl]-2-tert-butylanthracene,9,10-bis[2-(1-naphthyl)phenyl]anthracene, or2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene can be used.

Further alternatively, an aromatic hydrocarbon compound such as2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9′-bianthryl,10,10′-diphenyl-9,9′-bianthryl,10,10′-bis(2-phenylphenyl)-9,9′-bianthryl,10,10′-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9′-bianthryl, anthracene,tetracene, rubrene, perylene, 2,5,8,11-tetra(tert-butyl)perylene,pentacene, coronene, 4,4′-bis(2,2-diphenylvinyl)biphenyl (abbreviation:DPVBi), or 9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene(abbreviation: DPVPA) can be used.

Further, as the electron acceptor, organic compounds such as7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ) and chloranil; and transition metal oxides can be given. Inaddition, oxides of metals belonging to Group 4 to Group 8 of theperiodic table can also be given. Specifically, vanadium oxide, niobiumoxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide,manganese oxide, and rhenium oxide are preferable because they have ahigh electron-accepting property. Among the above, molybdenum oxide isespecially preferable because it is stable in the air, has lowhygroscopic property, and is easy to handle.

Note that the hole-injection layer 111 may be formed using a compositematerial of the above-described high molecular compound, such as PVK,PVTPA, PTPDMA, or Poly-TPD, and the above-described electron acceptor.

The hole-transport layer 112 is a layer containing a substance having ahigh hole-transport property. As the substance having a highhole-transport property, an aromatic amine compound such as NPB, TPD,4,4′-bis[N-(9,9-dimethylfluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: DFLDPBi), or4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB) can be used. The materials described here aremainly materials having a hole mobility of 10⁻⁶ cm²/Vs or higher.However, substances other than these can also be used as long as theyhave a hole-transport property higher than an electron-transportproperty. Note that the layer containing a substance having a highhole-transport property is not limited to a single layer, and a stackedlayer in which two or more layers containing the above-describedsubstance are stacked may be used.

Alternatively, for the hole-transport layer 112, a high molecularcompound such as PVK, PVTPA, PTPDMA, or Poly-TPD can be used.

The light-emitting layer 113 is preferably a layer containing theorganometallic complex which is one embodiment of the present invention,specifically, a layer containing, as a host, a substance which has ahigher triplet excitation energy than the organometallic complex whichis one embodiment of the present invention and the organometalliccomplex which is one embodiment of the present invention dispersed as aguest. Thus, quenching of light emission from the organometallic complexcaused due to the concentration can be prevented. Note that the tripletexcitation energy indicates an energy gap between a ground state and atriplet excited state.

Although there is no particular limitation on the substance used fordispersing any of the above-described organometallic complexes (i.e., ahost), a carbazole derivative such as CBP or4,4′,4″-tris(N-carbazolyl)triphenylamine (abbreviation: TCTA); and ametal complex such as bis[2-(2-hydroxyphenyl)pyridinato]zinc(abbreviation: Znpp₂), bis[2-(2-hydroxyphenyl)benzoxazolato]zinc(abbreviation: ZnBOX),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviation:BAlq), or tris(8-quinolinolato)aluminum (abbreviation: Alg₃) arepreferable in addition to a compound having an arylamine skeleton, suchas 2,3-bis(4-diphenylaminophenyl)quinoxaline (abbreviation: TPAQn) orNPB. Alternatively, a high molecular compound such as PVK can be used.

The electron-transport layer 114 is a layer containing a substancehaving a high electron-transport property. For the electron-transportlayer 114, metal complexes such as Alga,tris(4-methyl-8-quinolinolato)aluminum (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium (abbreviation: BeBq₂), BAlq,Zn(BOX)₂, or bis[2-(2′-hydroxyphenyl)pyridinato]zinc (abbreviation:Zn(BTZ)₂) can be given. Alternatively, a heteroaromatic compound such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),3-(4-tert-butylphenyl)-4-phenyl-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ), bathophenanthroline (abbreviation: BPhen),bathocuproine (abbreviation: BCP), or4,4′-bis(5-methylbenzoxazol-2-yl)stilbene (abbreviation: BzOs) can beused. Further alternatively, a high molecular compound such aspoly(2,5-pyridinediyl) (abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py) orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) can be used. The substances described here aremainly materials having an electron mobility of 10⁻⁶ cm²/Vs or more.Note that materials other than these may alternatively be used as longas they have an electron-transport property higher than a hole-transportproperty.

Further, the electron-transport layer is not limited to a single layer,and a stacked layer in which two or more layers containing any of theabove-described substances are stacked may be used.

The electron-injection layer 115 is a layer containing a substancehaving a high electron-injection property. For the electron-injectionlayer 115, an alkali metal, an alkaline earth metal, or a compoundthereof, such as lithium fluoride (LiF), cesium fluoride (CsF), calciumfluoride (CaF₂), or lithium oxide (LiOx), can be used. Alternatively, arare earth metal compound such as erbium fluoride (ErF₃) can be used.Further alternatively, the substances for forming the electron-transportlayer 114, which are described above, can be used.

Alternatively, a composite material in which an organic compound and anelectron donor (donor) are mixed may be used for the electron-injectionlayer 115. Such a composite material is excellent in anelectron-injection property and an electron-transport property becauseelectrons are generated in the organic compound by the electron donor.In this case, the organic compound is preferably a material excellent intransporting the generated electrons. Specifically, for example, thesubstances for forming the electron-transport layer 114 (e.g., a metalcomplex and a heteroaromatic compound), which are described above, canbe used. As the electron donor, a substance showing an electron-donatingproperty with respect to the organic compound may be used. Specifically,an alkali metal, an alkaline earth metal, and a rare earth metal arepreferable, and lithium, cesium, magnesium, calcium, erbium, ytterbium,and the like are given. In addition, alkali metal oxide or alkalineearth metal oxide such as lithium oxide, calcium oxide, barium oxide,and the like can be given. Lewis base such as magnesium oxide canalternatively be used. An organic compound such as tetrathiafulvalene(abbreviation: TTF) can alternatively be used.

Note that each of the above-described hole-injection layer 111,hole-transport layer 112, light-emitting layer 113, electron-transportlayer 114, and electron-injection layer 115 can be formed by a methodsuch as an evaporation method (e.g., a vacuum evaporation method), anink-jet method, or a coating method.

When the second electrode 103 functions as a cathode, it can be formedusing a metal, an alloy, an electrically-conductive compound, a mixturethereof, or the like having a low work function (preferably, a workfunction of 3.8 eV or less). Specifically, Al, silver, or the like canbe used besides an element belonging to Group 1 or Group 2 of theperiodic table, that is, an alkali metal such lithium (Li) or cesium(Cs) and an alkaline earth metal such as magnesium (Mg), calcium (Ca),or strontium (Sr); an alloy of the above metals (e.g., MgAg and AlLi); arare earth metal such as europium (Eu) or ytterbium (Yb); an alloy ofthe above metals, or the like.

Note that, in the case where in the EL layer 102, a layer formed incontact with the second electrode 103 is formed using a compositematerial in which the organic compound and the electron donor (donor),which are described above, are mixed, a variety of conductive materialssuch as Al, Ag, ITO, and indium tin oxide containing silicon or siliconoxide can be used regardless of the work function.

Note that the second electrode 103 can be formed by a vacuum evaporationmethod or a sputtering method. Alternatively, in the case of using asilver paste or the like, a coating method, an ink-jet method, or thelike can be used.

In the above-described light-emitting element, current flows due to apotential difference generated between the first electrode 101 and thesecond electrode 103 and holes and electrons recombine in the EL layer102, whereby light is emitted. Then, the emitted light is extractedoutside through one or both of the first electrode 101 and the secondelectrode 103. Therefore, one or both of the first electrode 101 and thesecond electrode 103 are electrodes having a light-transmittingproperty.

Note that by use of the light-emitting element described in thisembodiment, a passive matrix light-emitting device or an active matrixlight-emitting device in which the driving of the light-emitting elementis controlled by a thin film transistor (IFT) can be manufactured.

Note that there is no particular limitation on the structure of the TFTin the case of manufacturing the active matrix light-emitting device.For example, a staggered TFT or an inverted staggered TFT can be used asappropriate. Further, a driver circuit formed over a IFT substrate maybe formed of both an n-type TFT and a p-type TFT or only either ann-type TFT or a p-type TFT. Furthermore, there is also no particularlimitation on crystallinity of a semiconductor film used for the TFT.For example, an amorphous semiconductor film, a crystallinesemiconductor film, an oxide semiconductor film, or the like can beused.

Note that, in this embodiment, the organometallic complex of oneembodiment of the present invention, which is used for thelight-emitting layer 113, exhibits deep red emission with excellentcolor purity. Thus, a light-emitting element which exhibits deep redemission with excellent color purity can be obtained.

The structure described in Embodiment 2 can be combined with thestructure described in Embodiment 1 as appropriate.

Embodiment 3

The light-emitting element which is one embodiment of the presentinvention may include a plurality of light-emitting layers. A pluralityof light-emitting layers are provided and light is emitted from each ofthe light-emitting layers, whereby emission in which plural types oflight are mixed can be obtained. Thus, white light can be obtained, forexample. In this embodiment, an embodiment of a light-emitting elementincluding a plurality of light-emitting layers will be described withreference to FIG. 2.

In FIG. 2, an EL layer 202 including a first light-emitting layer 213and a second light-emitting layer 215 is provided between a firstelectrode 201 and a second electrode 203. Emission in which lightemitted from the first light-emitting layer 213 and light emitted fromthe second light-emitting layer 215 are mixed can be obtained. Aseparation layer 214 is preferably provided between the firstlight-emitting layer 213 and the second light-emitting layer 215.

When a voltage is applied so that the potential of the first electrode201 is higher than the potential of the second electrode 203, currentflows between the first electrode 201 and the second electrode 203, andholes and electrons recombine in the first light-emitting layer 213, thesecond light-emitting layer 215, or in the separation layer 214.Generated excitation energy is distributed to the first light-emittinglayer 213 and the second light-emitting layer 215 to bring each of afirst light-emitting substance contained in the first light-emittinglayer 213 and a second light-emitting substance contained in the secondlight-emitting layer 215 into an excited state. The excited first andsecond light-emitting substances emit light when returning to the groundstate.

The first light-emitting layer 213 contains the first light-emittingsubstance typified by a fluorescent compound such as perylene,2,5,8,11-tetra(tert-butyl)perylene (abbreviation: TBP), DPVBi,4,4′-bis[2-(N-ethylcarbazol-3-yl)vinyl]biphenyl (abbreviation: BCzVBi),BAlq, or bis(2-methyl-8-quinolinolato)galliumchloride (abbreviation:Gamq₂Cl); or a phosphorescent substance such asbis{2-[3,5-bis(trifluoromethyl)phenyl]pyridinato-N,C²′}iridium(III)picolinate(abbreviation: Ir(CF₃ ppy)₂(pic)),bis{2-(4,6-difluorophenyl)pyridinato-N,C²′}iridium(III)acetylacetonate(abbreviation: FIr(acac)),bis[2-(4,6-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)picolinate(abbreviation: FIrpic), or bis[2-(4,6-difuluorophenyl)pyridinato-N,C²′]iridium(III)tetra(1-pyrazolyl)borate (abbreviation:FIr6), from which emission having a peak at 450 nm to 510 nm in anemission spectrum (i.e., blue light to blue green light) can beobtained.

Further, in the case where the first light-emitting substance is afluorescent compound, the first light-emitting layer 213 preferably hasa structure in which a substance having a larger singlet excitationenergy than the first light-emitting substance is used as a first hostand the first light-emitting substance is dispersed as a guest. Further,in the case where the first light-emitting substance is a phosphorescentcompound, the first light-emitting layer 213 preferably has a structurein which a substance having a higher triplet excitation energy than thefirst light-emitting substance is used as a first host and the firstlight-emitting substance is dispersed as a guest. As the first host,DNA, t-BuDNA, or the like can be used in addition to the above-describedNPB, CBP, TCTA, and the like. Note that the singlet excitation energy isan energy difference between a ground state and a singlet excited state.In addition, the triplet excitation energy is an energy differencebetween a ground state and a triplet excited state.

On the other hand, the second light-emitting layer 215 contains theorganometallic complex which is one embodiment of the present inventionand can exhibit deep red emission. The second light-emitting layer 215may have a similar structure to the light-emitting layer 113 describedin Embodiment 2.

In addition, specifically, the separation layer 214 can be formed usingTPAQn, NPB, CBP, TCTA, Znpp₂, ZnBOX, or the like described above. Inthis way, with provision of the separation layer 214, a defect thatemission intensity of one of the first light-emitting layer 213 and thesecond light-emitting layer 215 is stronger than the other can beprevented. Note that the separation layer 214 is not necessarilyprovided, and it may be provided as appropriate such that the ratio inemission intensity of the first light-emitting layer 213 to the secondlight-emitting layer 215 can be adjusted.

Note that, in this embodiment, the organometallic complex which is oneembodiment of the present invention is used for the secondlight-emitting layer 215 and another light-emitting substance is usedfor the first light-emitting layer 213, whereas the organometalliccomplex which is one embodiment of the present invention may be used forthe first light-emitting layer 213 and another light-emitting substancemay be used for the second light-emitting layer 215.

Further, the light-emitting element in which two light-emitting layersare provided as illustrated in FIG. 2 is described in this embodiment;however, the number of the light-emitting layers is not limited to two,and may be, for example, three. Emission from each light-emitting layermay be mixed. As a result, for example, white color emission can beobtained.

Note that the first electrode 201 may have a structure similar to thatof the first electrode 101 described in Embodiment 2. In addition, thesecond electrode 203 may also have a structure similar to that of thesecond electrode 103 described in Embodiment 2.

Further, in this embodiment, as illustrated in FIG. 2, a hole-injectionlayer 211, a hole-transport layer 212, an electron-transport layer 216,and an electron-injection layer 217 are provided. As for structures ofthese layers, the structures of the respective layers described inEmbodiment 2 may be applied. However, these layers are not necessarilyprovided and may be provided according to element characteristics.

Note that the structure described in this embodiment can be combinedwith the structure described in Embodiment 1 or 2 as appropriate.

Embodiment 4

In this embodiment, as one embodiment of the present invention, astructure of a light-emitting element in which a plurality of EL layersare included (hereinafter, such a light-emitting element is referred toas a stacked-type element) will be described with reference to FIG. 3.This light-emitting element is a stacked-type light-emitting elementincluding a plurality of EL layers (a first EL layer 302 and a second ELlayer 303) between a first electrode 301 and a second electrode 304.Note that, although the structure in which two EL layers are formed isdescribed in this embodiment, a structure in which three or more ELlayers are formed may be employed.

In this embodiment, the first electrode 301 functions as an anode, andthe second electrode 304 functions as a cathode. Note that for the firstelectrode 301 and the second electrode 304, structures similar to thosedescribed in Embodiment 2 can be employed. In addition, although theplurality of EL layers (the first EL layer 302 and the second EL layer303) may have structures similar to those described in Embodiment 2, anyof the EL layers may have a structure similar to that described inEmbodiment 2. In other words, the structures of the first EL layer 302and the second EL layer 303 may be the same or different from each otherand can be similar to those described in Embodiment 2.

Further, a charge generation layer 305 is provided between the pluralityof EL layers (the first EL layer 302 and the second EL layer 303). Thecharge generation layer 305 has a function of injecting electrons intoone of the EL layers and injecting holes into the other of the EL layerswhen a voltage is applied to the first electrode 301 and the secondelectrode 304. In this embodiment, when a voltage is applied so that thepotential of the first electrode 301 is higher than that of the secondelectrode 304, the charge generation layer 305 injects electrons intothe first EL layer 302 and injects holes into the second EL layer 303.

Note that the charge generation layer 305 preferably has alight-transmitting property in terms of light extraction efficiency.Further, the charge generation layer 305 functions even if it has lowerconductivity than the first electrode 301 or the second electrode 304.

The charge generation layer 305 may have either a structure in which anelectron acceptor (acceptor) is added to an organic compound having ahigh hole-transport property or a structure in which an electron donor(donor) is added to an organic compound having a high electron-transportproperty. Alternatively, both of these structures may be stacked.

In the case of the structure in which an electron acceptor is added toan organic compound having a high hole-transport property, as theorganic compound having a high hole-transport property, for example, anaromatic amine compound such as NPB, TPD, TDATA, MTDATA, or4,4′-bis[N-(Spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), or the like can be used. The materials describedhere are mainly materials having a hole mobility of 10⁻⁶ cm²/Vs orhigher. However, substances other than the above substances may be usedas long as they are organic compounds having a hole-transport propertyhigher than an electron-transport property.

Further, as the electron acceptor,7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ), chloranil, and the like can be given. In addition, transitionmetal oxides can be given. Moreover, oxides of metals belonging toGroups 4 to 8 of the periodic table can be used. Specifically, vanadiumoxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide,tungsten oxide, manganese oxide, and rhenium oxide are preferablebecause they have high electron-accepting properties. Among these,molybdenum oxide is especially preferable because it is stable in theair, has low hygroscopic property, and is easy to handle.

On the other hand, in the case of the structure in which an electrondonor is added to an organic compound having a high electron-transportproperty, as the organic compound having a high electron-transportproperty, for example, a metal complex having a quinoline skeleton or abenzoquinoline skeleton, such as Alq, Almq₃, BeBq₂, or BAlq, or the likecan be used. Alternatively, a metal complex having an oxazole-basedligand or a thiazole-based ligand, such as Zn(BOX)₂ or Zn(BTZ)₂ can beused. Alternatively, in addition to such a metal complex, PBD, OXD-7,TAZ, BPhen, BCP, or the like can be used. The materials described hereare mainly materials having an electron mobility of 10⁻⁶ cm²/Vs orhigher. Note that substances other than the above substances may be usedas long as they are organic compounds having an electron-transportproperty higher than a hole-transport property.

Further, as the electron donor, an alkali metal, an alkaline earthmetal, a rare earth metal, a metal belonging to Group 13 of the periodictable, or an oxide or carbonate thereof can be used. Specifically,lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb),indium (In), lithium oxide, cesium carbonate, or the like is preferablyused. Alternatively, an organic compound such as tetrathianaphthacenemay be used as the electron donor.

Note that by formation of the charge generation layer 305 using any ofthe above materials, an increase in the drive voltage in the case wherethe EL layers are stacked can be suppressed.

Although the light-emitting element having two EL layers has beendescribed in this embodiment, the present invention can be similarlyapplied to a light-emitting element in which three or more EL layers arestacked. A plurality of EL layers are arranged to be separated from eachother with a charge generation layer between a pair of electrodes, likethe light-emitting element according to this embodiment, whereby anelement having a long lifetime and high luminance can be achieved withcurrent density kept low. When the light-emitting element is applied toa lighting device, a drop in voltage due to the resistance of anelectrode material can be suppressed, and thus uniform emission in alarge area can be achieved. Moreover, a light-emitting device which canbe driven at a low voltage and has low power consumption can beachieved.

Further, when the EL layers have different emission colors, a desiredemission color can be obtained from the whole light-emitting element.For example, in the light-emitting element having two EL layers, when anemission color of the first EL layer and an emission color of the secondEL layer are made to be complementary colors, it is possible to obtain alight-emitting element from which white light is emitted from the wholelight-emitting element. Note that “complementary color” refers to arelation between colors which become achromatic color by being mixed. Inother words, white emission can be obtained by mixture of light obtainedfrom substances whose emission colors are complementary colors.

Also in a light-emitting element having three EL layers, for example,white light can be similarly obtained from the whole light-emittingelement when an emission color of a first EL layer is red, an emissioncolor of a second EL layer is green, and an emission color of a third ELlayer is blue.

Note that the structure described in this embodiment can be used inappropriate combination with any structure described in Embodiments 1and 2.

Embodiment 5

In this embodiment, as one embodiment of the present invention, anembodiment of a light-emitting element in which an organometalliccomplex is used as a sensitizer will be described with reference to FIG.1.

FIG. 1 illustrates the light-emitting element in which the EL layer 102including the light-emitting layer 113 is interposed between the firstelectrode 101 and the second electrode 103. The light-emitting layer 113contains the organometallic complex which is one embodiment of thepresent invention and a fluorescent compound which can emit light with alonger wavelength than that of the light emitted from thisorganometallic complex.

In such a light-emitting element, holes injected from the firstelectrode 101 and electrons injected from the second electrode 103 siderecombine in the light-emitting layer 113 to bring the fluorescentcompound into an excited state. Light is emitted when the fluorescentcompound in the excited state returns to the ground state. In this case,the organometallic complex which is one embodiment of the presentinvention acts as a sensitizer for the fluorescent compound to increasethe number of molecules of the fluorescent compound in the singletexcited state. As described above, the organometallic complex of thepresent invention is used as a sensitizer, whereby a light-emittingelement with good emission efficiency can be obtained. Note that in thelight-emitting element of this embodiment, the first electrode 101functions as an anode and the second electrode 103 function as acathode.

The light-emitting layer 113 contains the organometallic complex whichis one embodiment of the present invention and the fluorescent compoundwhich can emit light with a longer wavelength than this organometalliccomplex. The light-emitting layer 113 may have a structure in which asubstance having a larger singlet excitation energy than the fluorescentsubstance as well as a higher triplet excitation energy than theorganometallic complex is used as a host, and the organometallic complexand the fluorescent compound are dispersed as a guest.

Note that there is no particular limitation on the substance used fordispersing the organometallic complex and the fluorescent compound(I.e., host), and the substances given as examples of the host inEmbodiment 2, or the like can be used.

Further, although there is also no particular limitation on thefluorescent compound, a compound which can exhibit emission of deep redlight to deep red infrared light, such as4-dicyanomethylene-2-isopropyl-6-[2-(1,1,7,7-tetramethyljulolidin-9-yl)ethenyl]-4H-pyran(abbreviation: DCJTI), magnesium phthalocyanine, magnesium porphyrin, orphthalocyanine, or the like is preferable.

Note that the first electrode 101 and the second electrode 103 describedin this embodiment may have structures similar to those of the firstelectrode and the second electrode described in Embodiment 2,respectively.

Further, the hole-injection layer 111, the hole-transport layer 112, theelectron-transport layer 114, and the electron-injection layer 115 areprovided as illustrated in FIG. 1 in this embodiment, and as forstructures of these layers, the structures of the respective layersdescribed in Embodiment 2 may be applied. However, these layers are notnecessarily provided and may be provided according to elementcharacteristics.

The above-described light-emitting element can emit light with highefficiency by use of the organometallic complex which is one embodimentof the present invention as a sensitizer.

Note that the structure described in this embodiment can be combinedwith any of the structures described in Embodiments 1 to 4 asappropriate.

Embodiment 6

In this embodiment, as one embodiment of the present invention, apassive matrix light-emitting device and an active matrix light-emittingdevice each of which is a light-emitting device manufactured using alight-emitting element will be described.

FIGS. 4A to 4D and FIG. 5 illustrate examples of passive matrixlight-emitting devices.

In a passive-matrix (also referred to as “simple-matrix”) light-emittingdevice, a plurality of anodes arranged in stripes (in stripe form) areprovided to be perpendicular to a plurality of cathodes arranged instripes, and a light-emitting layer is interposed at each intersection.Thus, a pixel at an intersection of an anode selected (to which avoltage is applied) and a cathode selected emits light.

FIGS. 4A to 4C are top views illustrating a pixel portion beforesealing. FIG. 4D is a cross-sectional view taken along the chain lineA-A′ in FIGS. 4A to 4C.

An insulating layer 402 is formed as a base insulating layer over asubstrate 401. Note that the insulating layer 402 is not necessarilyformed if the base insulating layer is not needed. A plurality of firstelectrodes 403 are arranged in stripes at regular intervals over theinsulating layer 402 (see FIG. 4A).

In addition, a partition wall 404 having openings each corresponding toa pixel is provided over the first electrodes 403. The partition wall404 having the openings is formed of an insulating material (aphotosensitive or nonphotosensitive organic material (e.g., polyimide,acrylic, polyamide, polyimide amide, resist, or benzocyclobutene) or anSOG film (e.g., a SiO_(x) film containing an alkyl group). Note that theopenings each corresponding to a pixel serve as light-emitting regions(see FIG. 4B).

A plurality of inversely-tapered partition walls 406 parallel to eachother are provided over the partition wall 404 having the openings tointersect with the first electrodes 403 (see FIG. 4C). Theinversely-tapered partition walls 406 are formed by a photolithographymethod using a positive-type photosensitive resin, portion of whichunexposed to light remains as a pattern, and by adjustment of the amountof light exposure or the length of development time so that a lowerportion of a pattern is etched more.

After the inversely-tapered partition walls 406 are formed asillustrated in FIG. 4C, EL layers 407 and second electrodes 408 aresequentially formed as illustrated in FIG. 4D. The total thickness ofthe partition wall 404 having the openings and the inversely-taperedpartition wall 406 is set to be larger than the total thickness of theEL layer 407 and the second electrode 408; thus, as illustrated in FIG.4D, EL layers 407 and second electrodes 408 which are separated forplural regions are formed. Note that the plurality of separated regionsare electrically isolated from one another.

The second electrodes 408 are electrodes in stripe form that areparallel to each other and extend along a direction intersecting withthe first electrodes 403. Note that a plurality of stacked layers eachincluding the EL layer 407 and part of conductive layer forming thesecond electrode 408 are also formed over the inversely-taperedpartition walls 406; however, they are separated from the EL layer 407and the second electrode 408.

Note that there is no particular limitation on the first electrode 403and the second electrode 408 in this embodiment as long as one of themis an anode and the other is a cathode. Note that a stacked structure inwhich the EL layer 407 is included may be adjusted as appropriate inaccordance with the polarity of the electrode.

Further, if necessary, a sealing material such as a sealing can or aglass substrate may be attached to the substrate 401 for sealing with anadhesive such as a sealant, so that the light-emitting element is placedin the sealed space. This can prevents deterioration of thelight-emitting element. Note that the sealed space may be filled with afiller or a thy inert gas. Furthermore, a desiccant or the like may beput between the substrate and the sealant in order to preventdeterioration of the light-emitting element due to moisture. Thedesiccant removes a minute amount of moisture, thereby achievingsufficient desiccation. The desiccant may be a substance which absorbsmoisture by chemical adsorption, such as an oxide of an alkaline earthmetal as typified by calcium oxide or barium oxide. Alternatively, thedesiccant may be a substance which adsorbs moisture by physicaladsorption such as zeolite or silica gel.

FIG. 5 is a top view of the case where the passive matrix light-emittingdevice illustrated in FIGS. 4A to 4D is mounted with an FPC and thelike.

In FIG. 5, scan lines and data lines are perpendicularly intersect witheach other in a pixel portion for displaying images.

Here, the first electrode 403, the second electrode 408, and theinversely-tapered partition wall 406 in FIGS. 4A to 4D correspond to ascan line 503, a data line 508, and a partition wall 506 in FIG. 5,respectively. The EL layers 407 in FIGS. 4A to 4D are interposed betweenthe data lines 508 and the scan lines 503, and an intersection portionindicated by a region 505 corresponds to one pixel.

Note that the scan lines 503 are electrically connected at their ends toconnection wirings 509, and the connection wirings 509 are connected toan FPC 511 b through an input terminal 510. In addition, the data linesare connected to an FPC 511 a through the input terminal 512.

If necessary, a polarizing plate, a circularly polarizing plate(including an elliptically polarizing plate), a retardation plate (aquarter-wave plate or a half-wave plate), or an optical film such as acolor filter may be provided as appropriate over a light-emittingsurface. Further, the polarizing plate or the circularly polarizingplate may be provided with an anti-reflection film. For example,anti-glare treatment may be carried out by which reflected light can bediffused by projections and depressions on the surface so as to deepreduce the glare.

Note that, although FIG. 5 illustrates an example in which a drivercircuit is not provided over the substrate, an IC chip including adriver circuit may be mounted on the substrate.

Further, in the case where the IC chip is mounted, a data line side ICand a scan line side IC, in each of which the driver circuit fortransmitting a signal to a pixel portion is formed, are mounted on theperiphery of (outside) the pixel portion by a COG method. The mountingmay be performed using TCP or a wire bonding method other than the COGmethod. TCP is a TAB tape mounted with an IC, and a TAB tape isconnected to a wiring over an element formation substrate and an IC ismounted. Each of the data line side IC and the scanning line side IC maybe formed using a silicon substrate, or may be formed by formation of adriver circuit with a TFT over a glass substrate, a quartz substrate, ora plastic substrate.

Next, an example of an active-matrix light-emitting device will bedescribed with reference to FIGS. 6A and 6B. Note that FIG. 6A is a topview illustrating a light-emitting device and FIG. 6B is across-sectional view taken along the chain line A-A′ in FIG. 6A. Theactive matrix light-emitting device according to this embodimentincludes a pixel portion 602 provided over an element substrate 601, adriver circuit portion (a source side driver circuit) 603, and a drivercircuit portion (a gate side driver circuit) 604. The pixel portion 602,the driver circuit portion 603, and the driver circuit portion 604 aresealed, with a sealing material 605, between the element substrate 601and a sealing substrate 606.

In addition, over the element substrate 601, a lead wiring 607 forconnecting an external input terminal, through which a signal (e.g., avideo signal, a clock signal, a start signal, a reset signal, or thelike) or an electric potential is transmitted to the driver circuitportion 603 and the driver circuit portion 604, is provided. Here, anexample is described in which a flexible printed circuit (FPC) 608 isprovided as the external input terminal. Although only an FPC is shownhere, this FPC may have a printed wiring board (PWB) attached. Thelight-emitting device in this specification includes not only alight-emitting device itself but also a light-emitting device with anFPC or a PWB attached.

Next, a cross-sectional structure will be described with reference toFIG. 6B. The driver circuit portion and the pixel portion are formedover the element substrate 601, and in FIG. 6B, the driver circuitportion 603 that is a source side driver circuit and the pixel portion602 are illustrated.

An example is illustrated in which a CMOS circuit which is a combinationof an n-channel 114T 609 and a p-channel T 610 is formed as the drivercircuit portion 603. Note that a circuit included in the driver circuitportion may be formed using various types of circuits such as CMOScircuits, PMOS circuits, or NMOS circuits. Although a driver integratedtype in which the driver circuit is formed over the substrate isdescribed in this embodiment, the driver circuit may not necessarily beformed over the substrate, and the driver circuit can be formed outside,not over the substrate.

The pixel portion 602 is formed of a plurality of pixels each of whichincludes a switching TFT 611, a current control TFT 612, and an anode613 which is electrically connected to a wiring (a source electrode or adrain electrode) of the current control TFT 612. Note that an insulator614 is formed to cover end portions of the anode 613. In thisembodiment, the insulator 614 is formed using a positive photosensitiveacrylic resin.

The insulator 614 is preferably formed so as to have a curved surfacewith curvature at an upper end portion or a lower end portion thereof inorder to obtain favorable coverage by a film which is to be stacked overthe insulator 614. For example, in the case of using a positivephotosensitive acrylic resin as a material for the insulator 614, theinsulator 614 is preferably formed so as to have a curved surface with acurvature radius (0.2 μm to 3 μm) at the upper edge portion. Note thateither a negative photosensitive material that becomes insoluble in anetchant by light irradiation or a positive photosensitive material thatbecomes soluble in an etchant by light irradiation can be used for theinsulator 614. As the insulator 614, without limitation to an organiccompound, either an organic compound or an inorganic compound such assilicon oxide or silicon oxynitride can be used.

An EL layer 615 and a cathode 616 are stacked over the anode 613. Notethat when an ITO film is used as the anode 613, and a stacked film of atitanium nitride film and a film containing aluminum as its maincomponent or a stacked film of a titanium nitride film, a filmcontaining aluminum as its main component, and a titanium nitride filmis used as the wiring of the current controlling TFT 612 which isconnected to the anode 613, resistance of the wiring is low andfavorable ohmic contact with the ITO film can be obtained. Note that,although not illustrated, the cathode 616 is electrically connected toan FPC 608 which is an external input terminal.

Note that in the EL layer 615, at least a light-emitting layer isprovided, and in addition to the light-emitting layer, a hole-injectionlayer, a hole-transport layer, an electron-transport layer, or anelectron-injection layer is provided as appropriate. A light-emittingelement 617 is formed of a stacked structure of the anode 613, the ELlayer 615, and the cathode 616.

Although the cross-sectional view of FIG. 6B illustrates only onelight-emitting element 617, a plurality of light-emitting elements arearranged in matrix in the pixel portion 602. Light-emitting elementswhich provide three kinds of emissions (R, G, and B) are selectivelyformed in the pixel portion 602, whereby a light-emitting device capableof full color display can be formed. Alternatively, a light-emittingdevice which is capable of full color display may be manufactured by acombination with color filters.

Further, the sealing substrate 606 is attached to the element substrate601 with the sealing material 605, whereby a light-emitting element 617is provided in a space 618 surrounded by the element substrate 601, thesealing substrate 606, and the sealing material 605. The space 618 maybe filled with an inert gas (such as nitrogen or argon), or the sealingmaterial 605.

Note that an epoxy-based resin is preferably used as the sealingmaterial 605. Such a material preferably allows as little moisture andoxygen as possible to penetrate. As the sealing substrate 606, a plasticsubstrate formed of FRP (fiberglass-reinforced plastics), PVF (polyvinylfluoride), a polyester film; polyester or acrylic; or the like can beused instead of a glass substrate or a quartz substrate.

In this way, an active matrix light-emitting device can be obtained.

Note that the structure described in Embodiment 6 can be combined withany of the structures described in Embodiments 1 to 5 as appropriate.

Embodiment 7

In this embodiment, examples of various electronic devices and lightingdevices, which are completed using the light-emitting device of oneembodiment of the present invention, will be described with reference toFIGS. 7A to 7E and FIG. 8.

As the electronic devices to which the light-emitting device is applied,for example, there are a television device (also referred to as TV or atelevision receiver), a monitor for a computer or the like, a camerasuch as a digital camera, a digital video camera, a digital photo frame,a cellular phone (also referred to as a cellular phone or a portabletelephone device), a portable game machine, a portable informationterminal, an audio playback device, and a large game machine such as apin-ball machine. Specific examples of these electronic devices andlighting device are illustrated in FIGS. 7A to 7E.

FIG. 7A illustrates an example of a television device 7100. In thetelevision device 7100, a display portion 7103 is incorporated in ahousing 7101. Images can be displayed by the display portion 7103, andthe light-emitting device can be used for the display portion 7103. Inaddition, here, the housing 7101 is supported by a stand 7105.

The television device 7100 can be operated by an operation switch of thehousing 7101 or a separate remote controller 7110. With operation keys7109 of the remote controller 7110, channels and volume can becontrolled and images displayed on the display portion 7103 can becontrolled. Furthermore, the remote controller 7110 may be provided witha display portion 7107 for displaying data output from the remotecontroller 7110.

Note that the television device 7100 is provided with a receiver, amodem, and the like. With the receiver, general television broadcastingcan be received. Furthermore, when the television device 7100 isconnected to a communication network by wired or wireless connection viathe modem, one-way (from a transmitter to a receiver) or two-way(between a transmitter and a receiver, between receivers, or the like)data communication can be performed.

FIG. 7B illustrates a computer, which includes a main body 7201, ahousing 7202, a display portion 7203, a keyboard 7204, an externalconnecting port 7205, a pointing device 7206, and the like. Thiscomputer is manufactured by using a light-emitting device for thedisplay portion 7203.

FIG. 7C illustrates a portable game machine, which includes twohousings, a housing 7301 and a housing 7302, which are connected with ajoint portion 7303 so that the portable game machine can be opened orfolded. A display portion 7304 is incorporated in the housing 7301 and adisplay portion 7305 is incorporated in the housing 7302. In addition,the portable game machine illustrated in FIG. 7C includes a speakerportion 7306, a recording medium insertion portion 7307, an LED lamp7308, an input means (an operation key 7309, a connection terminal 7310,a sensor 7311 (a sensor having a function of measuring force,displacement, position, speed, acceleration, angular velocity,rotational frequency, distance, light, liquid, magnetism, temperature,chemical substance, sound, time, hardness, electric field, current,voltage, electric power, radiation, flow rate, humidity, gradient,oscillation, odor, or infrared rays), or a microphone 7312), and thelike. It is needless to say that the structure of the portable gamesmachine is not limited to the above as long as the light-emitting deviceis used for at least either the display portion 7304 or the displayportion 7305, or both. The portable game machine illustrated in FIG. 7Chas a function of reading out a program or data stored in a storagemedium to display it on the display portion, and a function of sharinginformation with another portable game machine by wirelesscommunication. The portable game machine illustrated in FIG. 7C can havea variety of functions without limitation to the above.

FIG. 7D illustrates an example of a cellular phone. The cellular phone7400 is provided with a display portion 7402 incorporated in a housing7401, operation buttons 7403, an external connection port 7404, aspeaker 7405, a microphone 7406, and the like. Note that the cellularphone 7400 is manufactured using a light-emitting device for the displayportion 7402.

When the display portion 7402 of the cellular phone 7400 illustrated inFIG. 7D is touched with a finger or the like, data can be input into thecellular phone 7400. Further, operations such as making calls andcomposing e-mails can be performed by touching the display portion 7402with a finger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying an image. The secondmode is an input mode mainly for inputting information such ascharacters. The third mode is a display-and-input mode in which twomodes of the display mode and the input mode are mixed.

For example, in the case of making a call or composing an e-mail, a textinput mode mainly for inputting text is selected for the display portion7402 so that text displayed on a screen can be inputted. In that case,it is preferable to display a keyboard or number buttons on almost allthe area of the screen of the display portion 7402.

When a detection device including a sensor for detecting inclination,such as a gyroscope or an acceleration sensor, is provided inside thecellular phone 7400, display on the screen of the display portion 7402can be automatically changed by determining the orientation of thecellular phone 7400 (whether the cellular phone is placed horizontallyor vertically for a landscape mode or a portrait mode).

The screen modes are switched by touching the display portion 7402 oroperating the operation buttons 7403 of the housing 7401. Alternatively,the screen modes can be switched depending on kinds of images displayedon the display portion 7402. For example, when a signal for an imagedisplayed in the display portion is data of moving images, the screenmode is switched to the display mode. When the signal is text data, thescreen mode is switched to the input mode.

Moreover, in the input mode, when input by touching the display portion7402 is not performed within a specified period while a signal detectedby an optical sensor in the display portion 7402 is detected, the screenmode may be controlled so as to be switched from the input mode to thedisplay mode.

The display portion 7402 can function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken bytouching the display portion 7402 with the palm or the finger, wherebypersonal authentication can be performed. Furthermore, by provision of abacklight or a sensing light source emitting a near-infrared light forthe display portion, an image of a finger vein, a palm vein, or the likecan also be taken.

FIG. 7E illustrates a desk lamp, which includes a lighting portion 7501,a lampshade 7502, an adjustable arm 7503, a support 7504, a base 7505,and a power supply 7506. The desk lamp is manufactured using alight-emitting device for the lighting portion 7501. Note that thelighting device includes a ceiling light, a wall light, and the like inits category.

FIG. 8 illustrates an example in which the light-emitting device is usedfor an indoor lighting device 801. Since the light-emitting device canhave a larger area, the light-emitting device can be used as a lightingdevice having a large area. Alternatively, the light-emitting device canbe used as a roll-type lighting device 802. Note that as illustrated inFIG. 8, a desk lamp 803 described with reference to FIG. 7E may be usedtogether in a room provided with the indoor lighting device 801.

As described above, electronic devices and a lighting device can beobtained by application of the light-emitting device. Application rangeof the light-emitting device is so wide that the light-emitting devicecan be applied to electronic devices in a variety of fields.

Note that the structure described in this embodiment can be combinedwith any of the structures described in Embodiments 1 to 6 asappropriate.

Example 1 Synthesis Example

This example shows a synthesis method of(acetylacetonato)bis[2-(1-naphthyl)-3,5-dimethylpyrazinato)iridium(III)(abbreviation: [Ir(dm1npr)₂(acac)]), which is the organometallic complexof one embodiment of the present invention represented by StructuralFormula (100) in Embodiment 1. A structure of [Ir(dm1npr)₂(acac)] isshown below.

Step 1: Synthesis of 2-(1-naphthyl)-3,5-dimethylpyrazine (abbreviation:Hdm1npr)

First, into a recovery flask equipped with a reflux pipe were put 2.05 gof 2-chloro-3,5-dimethylpyrazine, 2.48 g of 1-naphthylboronic acid, 1.53g of sodium carbonate, 0.066 g ofbis(triphenylphosphine)palladium(II)dichloride (abbreviation:Pd(PPh₃)₂Cl₂), 15 mL of water, and 15 mL of acetonitrile, and the air inthe flask was replaced with argon. This reaction container was subjectedto irradiation with microwaves (2.45 GHz, 100 W) for 10 minutes, wherebyheating was performed. After that, water was added to this solution, andan organic layer was extracted with dichloromethane. The obtainedorganic layer was washed with water and dried with magnesium sulfate.After the drying, the solution was filtered. The solvent of thissolution was distilled off, and then the obtained residue was purifiedby silica gel column chromatography using dichloromethane as adeveloping solvent. Accordingly, Hdm1npr (a light orange powder, 59%yield), which was the substance to be produced, was obtained. Note thatthe irradiation with microwaves was performed using a microwavessynthesis system (Discover, produced by CEM Corporation). The synthesisscheme of Step 1 is shown in (a-1) below.

Step 2: Synthesis ofdi-μ-chloro-[bis{2-(1-naphthyl)-3,5-dimethylpyrazine}iridium(III)](abbreviation: [Ir(dm1npr)₂Cl]₂)

Next, into a recovery flask equipped with a reflux pipe were put 15 mLof 2-ethoxyethanol, 5 mL of water, 1.99 g of Hdm1npr obtained in aboveStep 1, and 1.27 g of iridium chloride hydrate (IrCl₃.H₂O) (produced bySigma-Aldrich Corporation), and the air in the flask was replaced withargon. After that, irradiation with microwaves (2.45 GHz, 100 W) wasperformed for 1 hour to cause a reaction. The reaction solution wasfiltered, and then the filtrate was concentrated and dried. The obtainedresidue was recrystallized from ethanol, whereby a dinuclear complex[Ir(dm1npr)₂Cl]₂ was obtained (a dark orange powder, 54% yield).Further, the synthesis scheme of Step 2 is shown in (b-2) below.

Step 3: Synthesis of(acetylacetonato)bis[2-(1-naphthyl)-3,5-dimethylpyrazinato]iridium(III)(abbreviation: [Ir(dm1npr)₂(acac)])>

Furthermore, into a recovery flask equipped with a reflux pipe were put20 mL of 2-ethoxyethanol, 1.60 g of the dinuclear complex[Ir(dm1npr)₂Cl]₂ obtained in above Step 2, 0.36 mL of acetylacetone, and1.22 g of sodium carbonate, and the air in the flask was replaced withargon. After that, irradiation with microwaves (2.45 GHz, 100 W) wasperformed for 30 minutes to cause a reaction. The reaction solution wasfiltered. The obtained solid was dissolved in dichloromethane. Thesolution was filtered to remove the insoluble portion, and thenrecrystallized from a mixed solvent of methanol and dichloromethane.Accordingly, a dark orange powder of the organometallic complex[Ir(dm1npr)₂(acac)], which is one embodiment of the present invention,was obtained (45% yield). The synthesis scheme of Step 3 is shown in(c-3) below.

Results of analysis of the dark orange powder obtained in above Step 3by nuclear magnetic resonance spectrometry (¹H NMR) are shown below. Inaddition, FIG. 9 is a ¹H NMR chart. According to the results, it wasfound that the organometallic complex [Ir(dm1npr)₂(acac)], which is oneembodiment of the present invention and represented by StructuralFormula (100) above, was obtained in this example.

¹H NMR. δ (CDCl₃): 1.79 (s, 6H), 2.66 (s, 6H), 2.72 (s, 6H), 5.26 (s,1H), 6.15 (brm, 2H), 7.17 (d, 2H), 7.24 (m, 2H), 7.39 (t, 2H), 7.65 (m,4H), 8.19 (s, 2H).

Next, [Irtdm1npr)₂(acac)] was analyzed by an ultraviolet-visible (UV)absorption spectroscopy. The UV spectrum was measured using anultraviolet-visible spectrophotometer (V550, produced by JASCOCorporation) at room temperature by use of a dichloromethane solution(0.076 mmol/L). In addition, an emission spectrum of [Ir(dm1npr)₂(acac)]was measured. The emission spectrum was measured by a fluorescencespectrophotometer (FS920, produced by Hamamatsu Photonics Corporation)using a degassed dichloromethane solution (0.27 mmol/L) at roomtemperature. FIG. 10 shows the measurement results. The horizontal axisindicates wavelength, and the vertical axis indicates absorptionintensity and the emission intensity.

As shown in FIG. 10, the organometallic complex [Ir(dm1npr)₂(acac)]which is one embodiment of the present invention has a peak of emissionat 680 nm, and deep red light was observed from the dichloromethanesolution.

Example 2

A light-emitting element (Light-emitting Element 2) will be described inwhich the organometallic complex [Irtdm1npr)₂(acac)] (Structural Formula(100)), which is one embodiment of the present invention and synthesizedin Example 1, is used as a light-emitting substance. Further, as areference light-emitting element, a light-emitting element(Light-emitting Element 1) will also be described in which alight-emitting substance represented by Structural Formula (I) below isused as a light-emitting substance. Note that structures of otherorganic compounds used in this example are represented by StructuralFormulas (II) to (v). In addition, element structures of thelight-emitting elements will be described on the basis of FIG. 11.

<<Manufacture of Light-Emitting Elements 1 and 2>>

First, as a first electrode 1101, indium tin oxide containing siliconoxide (ITSO) is formed to a thickness of 110 nm over a substrate 1100made of glass. Note that the periphery of the ITSO is covered with aninsulating film so that a surface of the ITSO of 2 mm×2 mm is exposed.Here, the first electrode 1101 is an electrode that functions as ananode of the light-emitting element.

Next, as pretreatment for forming the light-emitting element over thesubstrate 1100, the surface of the substrate was washed, baked at 200°C. for one hour, and subjected to UV ozone treatment for 370 seconds.

After that, the substrate 1100 was transferred into a vacuum evaporationapparatus where the pressure had been reduced to approximately 10⁻⁴ Pa,and subjected to vacuum baking at 170° C. for 30 minutes in a heatingchamber of the vacuum evaporation apparatus, and then the substrate 1100was cooled down for about 30 minutes.

Next, the substrate 1100 was fixed to a holder provided in the vacuumevaporation apparatus so that a surface of the substrate 1100 over whichthe first electrode 1101 was formed faced downward. In this example, ahole-injection layer 1111, a hole-transport layer 1112, a light-emittinglayer 1113, an electron-transport layer 1114, and an electron-injectionlayer 1115 which are included in an EL layer 1102 are sequentiallyformed.

After reducing the pressure of the vacuum evaporation apparatus to 10⁻⁴Pa, NPB represented by the above Structural Formula (II) andmolybdenum(VI) oxide were co-evaporated with a mass ratio of NPB tomolybdenum(VI) oxide being 4:1, whereby the hole-injection layer 1111was formed. The thickness of the hole-injection layer 1111 was 50 nm.Note that the co-evaporation is an evaporation method in which somedifferent substances are evaporated from some different evaporationsources at the same time.

Next, NPB was evaporated to a thickness of 10 nm as the hole-transportlayer 1112.

Next, the light-emitting layer 1113 was formed over the hole-transportlayer 1112. In the case of Light-emitting Element 1, YGAO11 representedby the above Structural Formula (iii) and [Ir(dm2npr)₂(acac)]represented by the above Structural Formula (I) were co-evaporated overthe hole-transport layer 1112 with a mass ratio of YGAO11 to[Ir(dm2npr)₂(acac)] being 1:0.025 so that the light-emitting layer 1113was formed. In the case of Light-emitting Element 2, YGAO11 and[Ir(dm1npr)₂(acac)] represented by the above Structural Formula (100)were co-evaporated over the hole-transport layer 1112 with a mass ratioof YGAO11 to [Ir(dm1npr)₂(acac)] being 1:0.025 so that thelight-emitting layer 1113 was formed. The thickness of thelight-emitting layer 1113 in each element was 30 nm.

Next, after evaporating BAlq represented by the above Structural Formula(Iv) to a thickness of 10 nm, BPhen represented by the above StructuralFormula (v) was further evaporated to a thickness of 40 nm, whereby theelectron-transport layer 1114 was formed. Furthermore, lithium fluoridewas evaporated to a thickness of 2 nm over the electron-transport layer1114, whereby the electron-injection layer 1115 was formed.

Next, aluminum was deposited to a thickness of 200 nm as a secondelectrode 1103. Thus, the light-emitting elements (Light-emittingElements 1 and 2) each of which is one embodiment of the presentinvention were obtained. Note that the second electrode 1103 is anelectrode that functions as a cathode. In the above evaporation steps,evaporation was all performed by a resistance heating method.

Further, these light-emitting elements were sealed in a glove box undera nitrogen atmosphere to prevent being exposed to the atmosphere.

<<Operation characteristics of Light-emitting Elements 1 and 2>>

Operation characteristics of each of the manufactured light-emittingelements (Light-emitting Elements 1 and 2) were measured. Note that themeasurement was carried out at room temperature (under an atmosphere inwhich the temperature was kept at 25° C.).

FIG. 12 shows current density-luminance characteristics of eachlight-emitting element. In FIG. 12, the vertical axis representsluminance (cd/m²) and the horizontal axis represents current density(mA/cm²). FIG. 13 shows voltage-luminance characteristics of eachlight-emitting element. In FIG. 13, the vertical axis representsluminance (cd/m²) and the horizontal axis represents voltage (V).

FIG. 14 shows emission spectra obtained when the respectivelight-emitting elements were supplied with a current at a currentdensity of 25 mA/cm². As shown in FIG. 14, Light-emitting Elements 1 and2 have peaks of emission spectra at 591 nm and 638 nm, respectively,indicating that Light-emitting Element 2 exhibits red emission withhigher color purity than Light-emitting Element 1 which exhibits orangeemission. It was also found that the emission spectrum of Light-emittingElement 2 is derived from emission of the organometallic complex[Ir(dm1npr)₂(acac)] which is one embodiment of the present invention.

This application is based on Japanese Patent Application serial no.2009-232961 filed with the Japan Patent Office on Oct. 7, 2009, theentire contents of which are hereby incorporated by reference.

1-57. (canceled)
 58. A light-emitting element comprising anorganometallic complex, the organometallic complex comprising astructure represented by General Formula (G1):

R¹ and R² individually represent any of an alkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkylthiogroup having 1 to 4 carbon atoms, or an alkoxycarbonyl group having 1 to5 carbon atoms; R³ represents hydrogen or an alkyl group having 1 to 4carbon atoms; R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ individually represent any ofhydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy grouphaving 1 to 4 carbon atoms, a halogen group, a haloalkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms; and Mis a central metal and represents either a Group 9 element or a Group 10element.
 59. The light-emitting element according to claim 58, whereinthe structure is represented by General Formula (G3):

R¹ and R² individually represent any of an alkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkylthiogroup having 1 to 4 carbon atoms, or an alkoxycarbonyl group having 1 to5 carbon atoms; R⁵ represents any of hydrogen, an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogengroup, a haloallyl group having 1 to 4 carbon atoms, or an aryl grouphaving 6 to 12 carbon atoms; and M is a central metal and representseither a Group 9 element or a Group 10 element.
 60. The light-emittingelement according to claim 58, wherein the light-emitting element isapplied to an electronic device selected from the group consisting of atelevision device, a computer, a portable game machine, a cellularphone, and a lighting device.
 61. A light-emitting element comprising anorganometallic complex represented by General Formula (G4):

wherein: R¹ and R² individually represent any of an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, analkylthio group having 1 to 4 carbon atoms, or an alkoxycarbonyl grouphaving 1 to 5 carbon atoms; R³ represents hydrogen or an alkyl grouphaving 1 to 4 carbon atoms; R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ individuallyrepresent any of hydrogen, an alkyl group having 1 to 4 carbon atoms, analkoxy group having 1 to 4 carbon atoms, a halogen group, a haloalkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 12 carbonatoms; M is a central metal and represents either a Group 9 element or aGroup 10 element; L represents a monoanionic ligand; and n is 2 when thecentral metal is the Group 9 element or n is 1 when the central metal isthe Group 10 element.
 62. The light-emitting element according to claim61, wherein the organometallic complex is represented by General Formula(G6):

R¹ and R² individually represent any of an alkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkylthiogroup having 1 to 4 carbon atoms, or an alkoxycarbonyl group having 1 to5 carbon atoms; R⁵ represents any of hydrogen, an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogengroup, a haloalkyl group having 1 to 4 carbon atoms, or an aryl grouphaving 6 to 12 carbon atoms; M is a central metal and represents eithera Group 9 element or a Group 10 element; L represents a monoanionicligand; n is 2 when the central metal is the Group 9 element or n is 1when the central metal is the Group 10 element.
 63. The light-emittingelement according to claim 61, wherein the monoanionic ligand is any ofa monoanionic bidentate chelate ligand having a beta-diketone structure,a monoanionic bidentate chelate ligand having a carboxyl group, amonoanionic bidentate chelate ligand having a phenolic hydroxyl group,and a monoanionic bidentate chelate ligand in which two ligand elementsare both nitrogen.
 64. The light-emitting element according to claim 61,wherein the monoanionic ligand is represented by any of StructuralFormulas (L1) to (L6),

R¹⁰ to R²⁹ individually represent any of hydrogen, an alkyl group having1 to 4 carbon atoms, a halogen group, a haloalkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or anallylthio group having 1 to 4 carbon atoms; and A¹, A², and A³individually represent nitrogen N or carbon C—R; and R represents any ofhydrogen, an alkyl group having 1 to 4 carbon atoms, a halogen group, ora haloalkyl group having 1 to 4 carbon atoms.
 65. The light-emittingelement according to claim 61, wherein the light-emitting element isapplied to an electronic device selected from the group consisting of atelevision device, a computer, a portable game machine, a cellularphone, and a lighting device.
 66. A light-emitting element comprising anorganometallic complex represented by General Formula (G7):

wherein: R¹ and R² individually represent any of an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, analkylthio group having 1 to 4 carbon atoms, or an alkoxycarbonyl grouphaving 1 to 5 carbon atoms; R³ represents hydrogen or an alkyl grouphaving 1 to 4 carbon atoms; R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ individuallyrepresent any of hydrogen, an alkyl group having 1 to 4 carbon atoms, analkoxy group having 1 to 4 carbon atoms, a halogen group, a haloalkylgroup having 1 to 4 carbon atoms, or an aryl group having 6 to 12 carbonatoms; M is a central metal and represents either a Group 9 element or aGroup 10 element; and n is 2 when the central metal is the Group 9element or n is 1 when the central metal is the Group 10 element. 67.The light-emitting element according to claim 66, wherein theorganometallic complex is represented by General Formula (G9):

R¹ and R² individually represent any of an alkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkylthiogroup having 1 to 4 carbon atoms, or an alkoxycarbonyl group having 1 to5 carbon atoms; R⁵ represents any of hydrogen, an alkyl group having 1to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogengroup, a haloallyl group having 1 to 4 carbon atoms, or an aryl grouphaving 6 to 12 carbon atoms; M is a central metal and represents eithera Group 9 element or a Group 10 element; and n is 2 when the centralmetal is the Group 9 element or n is 1 when the central metal is theGroup 10 element.
 68. The light-emitting element according to claim 66,wherein the light-emitting element is applied to an electronic deviceselected from the group consisting of a television device, a computer, aportable game machine, a cellular phone, and a lighting device.
 69. Anorganometallic complex comprising a structure represented by GeneralFormula (G1):

wherein: R¹ represents any of an alkyl group having 1 to 4 carbon atoms,an alkoxy group having 1 to 4 carbon atoms, an alkylthio group having 1to 4 carbon atoms, or an alkoxycarbonyl group having 1 to 5 carbonatoms; R² represents any of hydrogen, an alkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an allylthiogroup having 1 to 4 carbon atoms, or an alkoxycarbonyl group having 1 to5 carbon atoms; R³ represents hydrogen or an alkyl group having 1 to 4carbon atoms; R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ individually represent any ofhydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy grouphaving 1 to 4 carbon atoms, a halogen group, a haloalkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms; and Mis a central metal and represents either a Group 9 element or a Group 10element.
 70. The organometallic complex according to claim 69, whereinthe structure is represented by General Formula (G3):

R¹ represents any of an alkyl group having 1 to 4 carbon atoms, analkoxy group having 1 to 4 carbon atoms, an allylthio group having 1 to4 carbon atoms, or an alkoxycarbonyl group having 1 to 5 carbon atoms;R² represents any of hydrogen, an alkyl group having 1 to 4 carbonatoms, an alkoxy group having 1 to 4 carbon atoms, an alkylthio grouphaving 1 to 4 carbon atoms, or an alkoxycarbonyl group having 1 to 5carbon atoms; R⁵ represents any of hydrogen, an alkyl group having 1 to4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogengroup, a haloalkyl group having 1 to 4 carbon atoms, or an aryl grouphaving 6 to 12 carbon atoms; and M is a central metal and representseither a Group 9 element or a Group 10 element.
 71. The organometalliccomplex according to claim 69, wherein the central metal is iridium orplatinum.
 72. A light-emitting element comprising the organometalliccomplex according to claim
 69. 73. The light-emitting element accordingto claim 72, wherein the light-emitting element is applied to anelectronic device selected from the group consisting of a televisiondevice, a computer, a portable game machine, a cellular phone, and alighting device.
 74. An organometallic complex represented by GeneralFormula (G4):

wherein: R¹ represents any of an alkyl group having 1 to 4 carbon atoms,an alkoxy group having 1 to 4 carbon atoms, an alkylthio group having 1to 4 carbon atoms, or an alkoxycarbonyl group having 1 to 5 carbonatoms; R² represents any of hydrogen, an alkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkylthiogroup having 1 to 4 carbon atoms, or an alkoxycarbonyl group having 1 to5 carbon atoms; R³ represents hydrogen or an alkyl group having 1 to 4carbon atoms; R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ individually represent any ofhydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy grouphaving 1 to 4 carbon atoms, a halogen group, a haloalkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms; M is acentral metal and represents either a Group 9 element or a Group 10element; L represents a monoanionic ligand; and n is 2 when the centralmetal is the Group 9 element or n is 1 when the central metal is theGroup 10 element.
 75. The organometallic complex according to claim 74,wherein the organometallic complex is represented by General Formula(G6):

R¹ represents any of an alkyl group having 1 to 4 carbon atoms, analkoxy group having 1 to 4 carbon atoms, an alkylthio group having 1 to4 carbon atoms, or an alkoxycarbonyl group having 1 to 5 carbon atoms;R² represents any of hydrogen, an alkyl group having 1 to 4 carbonatoms, an alkoxy group having 1 to 4 carbon atoms, an alkylthio grouphaving 1 to 4 carbon atoms, or an alkoxycarbonyl group having 1 to 5carbon atoms; R⁵ represents any of hydrogen, an alkyl group having 1 to4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogengroup, a haloallyl group having 1 to 4 carbon atoms, or an aryl grouphaving 6 to 12 carbon atoms; M is a central metal and represents eithera Group 9 element or a Group 10 element; L represents a monoanionicligand; n is 2 when the central metal is the Group 9 element or n is 1when the central metal is the Group 10 element.
 76. The organometalliccomplex according to claim 74, wherein the monoanionic ligand is any ofa monoanionic bidentate chelate ligand having a beta-diketone structure,a monoanionic bidentate chelate ligand having a carboxyl group, amonoanionic bidentate chelate ligand having a phenolic hydroxyl group,and a monoanionic bidentate chelate ligand in which two ligand elementsare both nitrogen.
 77. The organometallic complex according to claim 74,wherein the monoanionic ligand is represented by any of StructuralFormulas (L1) to (L6).

R¹⁰ to R²⁹ individually represent any of hydrogen, an alkyl group having1 to 4 carbon atoms, a halogen group, a haloalkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or analkylthio group having 1 to 4 carbon atoms; and A¹, A², and A³individually represent nitrogen N or carbon C—R; and R represents any ofhydrogen, an alkyl group having 1 to 4 carbon atoms, a halogen group, ora haloalkyl group having 1 to 4 carbon atoms.
 78. The organometalliccomplex according to claim 74, wherein the central metal is iridium orplatinum.
 79. A light-emitting element comprising the organometalliccomplex according to claim
 74. 80. The light-emitting element accordingto claim 79, wherein the light-emitting element is applied to anelectronic device selected from the group consisting of a televisiondevice, a computer, a portable game machine, a cellular phone, and alighting device.
 81. An organometallic complex represented by GeneralFormula (G7):

wherein: R¹ represents any of an alkyl group having 1 to 4 carbon atoms,an alkoxy group having 1 to 4 carbon atoms, an alkylthio group having 1to 4 carbon atoms, or an alkoxycarbonyl group having 1 to 5 carbonatoms; R² represents any of hydrogen, an alkyl group having 1 to 4carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkylthiogroup having 1 to 4 carbon atoms, or an alkoxycarbonyl group having 1 to5 carbon atoms; R³ represents hydrogen or an alkyl group having 1 to 4carbon atoms; R⁴, R⁵, R⁶, R⁷, R⁸, and R⁹ individually represent any ofhydrogen, an alkyl group having 1 to 4 carbon atoms, an alkoxy grouphaving 1 to 4 carbon atoms, a halogen group, a haloalkyl group having 1to 4 carbon atoms, or an aryl group having 6 to 12 carbon atoms; M is acentral metal and represents either a Group 9 element or a Group 10element; and n is 2 when the central metal is the Group 9 element or nis 1 when the central metal is the Group 10 element.
 82. Theorganometallic complex according to claim 81, wherein the organometalliccomplex is represented by General Formula (G9):

R¹ represents any of an alkyl group having 1 to 4 carbon atoms, analkoxy group having 1 to 4 carbon atoms, an alkylthio group having 1 to4 carbon atoms, or an alkoxycarbonyl group having 1 to 5 carbon atoms;R² represents any of hydrogen, an alkyl group having 1 to 4 carbonatoms, an alkoxy group having 1 to 4 carbon atoms, an alkylthio grouphaving 1 to 4 carbon atoms, or an alkoxycarbonyl group having 1 to 5carbon atoms; R⁵ represents any of hydrogen, an alkyl group having 1 to4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a halogengroup, a haloallyl group having 1 to 4 carbon atoms, or an aryl grouphaving 6 to 12 carbon atoms; M is a central metal and represents eithera Group 9 element or a Group 10 element; and n is 2 when the centralmetal is the Group 9 element or n is 1 when the central metal is theGroup 10 element.
 83. The organometallic complex according to claim 81,wherein the central metal is iridium or platinum.
 84. A light-emittingelement comprising the organometallic complex according to claim
 81. 85.The light-emitting element according to claim 84, wherein thelight-emitting element is applied to an electronic device selected fromthe group consisting of a television device, a computer, a portable gamemachine, a cellular phone, and a lighting device.